Assertion (A): Plants carry out photosynthesis during the day and respiration at night. Reason (R): Photosynthesis requires light, while respiration occurs continuously. MCQ with Answer and Explanation

Question

Assertion (A): Plants carry out photosynthesis during the day and respiration at night.
Reason (R): Photosynthesis requires light, while respiration occurs continuously.

A. Both A and R are true, and R is the correct explanation.

B. A is false, but R is true.

C. A is true, but R is false.

D. Both A and R are true, but R is not the correct explanation.

Answer: Option B

Solution (By JKExamLibrary)

Respiration occurs 24/7, while photosynthesis only in light. The statement implies they alternate, which is false. R is true: photosynthesis needs light, respiration is continuous. So A is false, R true.

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Question #1

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The 'Hormone Cholecystokinin' (CCK) is secreted by the I cells of the duodenal mucosa in response to the presence of fats and proteins. Its primary actions include:

A. Inhibiting the release of bile

B. Inhibiting gastric emptying and stimulating the gall bladder to contract and the pancreas to secrete digestive enzymes

C. Increasing blood glucose levels

D. Stimulating gastric acid secretion

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Correct Answer: Option B

Explanation:
Cholecystokinin (CCK) is a peptide hormone released by the I cells of the duodenum when acidic chyme containing fats (lipids) and partially digested proteins enters from the stomach. CCK has two major digestive actions: 1) It stimulates the gall bladder to contract, releasing stored bile into the duodenum to emulsify fats. 2) It stimulates the pancreatic acinar cells to secrete a juice rich in digestive enzymes (lipases, proteases, amylase). It also slows down gastric emptying, allowing more time for digestion in the small intestine.

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Question #2

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Which of the following statements about pollination is correct?

A. Hydrophily is pollination by insects.

B. Entomophily is pollination by wind.

C. Cross-pollination increases genetic variation.

D. Self-pollination always requires external agents.

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Correct Answer: Option C

Explanation:
Cross-pollination between different plants promotes genetic diversity. Self-pollination does not need external agents; entomophily is by insects, hydrophily by water, anemophily by wind.

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Question #3

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Consider statements about cell division: 1. Cytokinesis in plant cells occurs by cell plate formation. 2. Meiosis maintains the chromosome number. 3. Mitosis occurs in somatic cells. Which are correct?

A. 1 and 3 only

B. 2 and 3 only

C. 1, 2 and 3

D. 1 and 2 only

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Correct Answer: Option A

Explanation:
In plant cells, which have rigid cell walls, cytokinesis occurs by the formation of a new cell wall (cell plate) in the middle of the cell. Mitosis is equational division occurring in somatic cells for growth and repair, maintaining the same chromosome number. Meiosis is reductional division, halving the chromosome number to produce gametes. Thus, statements 1 and 3 are correct.

This question belongs to: Science Biology

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